Enhancing the life of an electrical transformer is an essential part of a modern power operation technology. The aging or deterioration of insulating oil is normally associated with oxidation. Due to the presence of oxygen and water, insulating oil oxidizes even under ideal conditions. The insulating properties of the oil are also affected by contaminants from the solid materials in the transformer dissolving in the oil. The reaction between unstable hydrocarbons in the oil and oxygen, moisture or other chemicals in the atmosphere, with the assistance of accelerators such as heat, results in decay products in the oil. Mineral oil insulating fluids undergo oxidative degradation in the presence of oxygen to give a number of oxidation products. The final products of oxidation are acidic materials that can affect the characteristics of the insulating fluid as well as damage the components of the electrical unit. The high temperatures in due course cause the fluid to oxidize and ultimately produce sludge and soluble acid in sufficient quantity to impair its heat transfer and dielectric efficiency. Sludge formation is the terminal stage of the deterioration process. The acids formed in the process of oxidation attack on the cellulose fibers and metals forming metallic soaps, lacquers, aldehydes, alcohols and ketones which precipitate as heavy tarry acidic sludge on the insulation. Sludge appears faster in heavily loaded, hot running and abused transformers causing shrinkage of the insulation through leaching out varnishes and cellulose materials.
The main purpose of transformer oil is to insulate and cool the transformer. A specification is a good start, but to successfully find just the right oil for transformer, details are needed. All transformers and their requirements are different. And right oils are needed that are tailored for each transformer's need for availability, performance and its geographical conditions. The Naphthenic oils are the best, which have outstanding properties for use in a transformer. Much due to their low viscosity at high temperatures and excellent solvency at very low temperatures. They also have high oxidation stability and great electrical properties that make them the perfect choice for a transformer.
In the prior art for producing Insulating fluids, generally, mineral oils or mineral oil with synthetic fluids or synthetic fluid alone were used. The focus has been on the use of such oil base to enhance the performance.
Reference may be made to U.S. Pat. No. 6,726,857 and U.S. Pat. No. 6,485,659 Goedde, et al. Apr. 27, 2004 Cooper Industries, Inc. (Houston, Tex.) Dielectric fluid having defined chemical composition for use in electrical apparatus. The dielectric coolants for use in sealed, non-vented transformers, and have improved performance characteristics, including decreased degradation of the paper insulating layers, as well as a greater degree of safety and environmental acceptability. This consist of aromatic hydrocarbons (di or tri aryl ethane such as biphenyl ethane or ethyl naphthalene), polyalphaolefins, polyol esters, and natural vegetable oils, along with additives to improve pour point, increase stability and reduce oxidation rate. (blend of mineral oil, polyalphaolefins, polyol esters and natural vegetable oils)
Reference may be made to U.S. Pat. No. 6,645,404 Oommen, et al. Nov. 11, 2003 ABB Technology AG (Zurich, CH) High oleic acid oil compositions and methods of making and electrical insulation fluids and devices comprising the same. High oleic acid triglyceride having the properties of a dielectric strength of at least 35 KV/100 mil gap, a dissipation factor of less than 0.05% at 25 NC., acidity of less than 0.03 mg KOH/g, electrical conductivity of less than 1 pS/m at 25 NC., a flash point of at least 250 NC. and a pour point of at least −15 NC with additives are disclosed as electrical insulation fluids.
Reference may be made to U.S. Pat. No. 6,340,658 Cannon, et al. Jan. 22, 2002 Wavely Light and Power (Waverly, Iowa) Vegetable-based transformer oil and transmission line fluid. A vegetable oil-based electrically-insulating fluid is environmentally-friendly and has a high flash point and a high fire point. The base oil is hydrogenated to produce maximum possible stability of the oil, or alternatively, is a higher oleic acid oil. The vegetable oils of the preferred embodiments are soybean or corn oils. The oil can be winterized to remove crystallized fats and improve the pour point of the base oil, without the necessity of heating the oil. The base oil can also be combined with an additive package containing materials specifically designed for improved pour point, improved cooling properties, and improved dielectric stability. The fluid is useful in electrical components such as transformers and transmission lines. It also provides methods for making the fluid and fluid-filled electrical components.
A patent filled by the inventors of the present invention disclosed the use of Heavy Alkyl Benzene alkaline earth metal sulfonates are in use as detergent-dispersant-anti rust additive in various types of lubricants (Patent application IPA number 1306/DEL/1998 & 1307/DEL/1998 by A. K. Singh et al assigned to CSIR). The alkyl benzenes are mono, di and poly substituted alkyl aromatics having one benzene or toluene aromatic ring and straight or branched paraffinic chains having carbon atoms 1 to 15 preferably 10 to 15, preferably mono and di alkyl benzene. Alkyl benzenes are produced as by-products during the preparation of, (1) linear alkyl benzene (LAB) in detergent industry, (2) heavy aromatic produced in catalytic reformer, and (3) naphtha or gas steam cracker liquid product. Alkyl benzene consists of substituted benzenes and no poly-aromatics/condensed ring or olefinic compounds are present in the alkyl benzenes. It can be used as an alternate to mineral base stock of lubricants. It will reduce the hazard potential of the lubricants. It will provide required properties such as good insulating, dissipation of heat, stability, anti-corrosion properties and more eco-friendliness.
There is a need for developing new insulating fluid composition, which is free from harmful polynuclear aromatic hydrocarbons generally found in mineral oil and produce less pollution. These objectives must be met, while simultaneously satisfying stringent performance standards, e.g., good insulation, dissipation of heat, stability and anti-corrosion.